Assume that 20 parts are checked each hour and that X denotes the number of parts in the sample of 20 that require rework. Parts are assumed to be independent with respect to rework.

(a) If the percentage of parts that require rework remains at 1%, what is the probability that hour 10 is the first sample at which X exceeds 1?

(b) If the rework percentage increases to 4%, what is the prob- ability that hour 10 is the first sample at which X'exceeds 1?

(e) If the rework percentage increases to 4%, what is the expected number of hours until. Y exceeds 1?